Recently, there has been considerable interest within the detergent industry for laundry detergents which are "compact" and therefore, have low dosage volumes. To facilitate production of these so-called low dosage detergents, many attempts have been made to produce high bulk density detergents, for example with a density of 600 g/l or higher. The low dosage detergents are currently in high demand as they conserve resources and can be sold in small packages which are more convenient for consumers.
Generally, them are two primary types of processes by which detergent granules or powders can be prepared. The first type of process involves spray-drying an aqueous detergent slurry in a spray-drying tower to produce highly porous detergent granules. In the second type of process, the various detergent components are dry mixed after which they are agglomerated with a binder such as a nonionic or anionic surfactant. In both processes, the most important factors which govern the density of the resulting detergent granules are the density, porosity and surface area of the various starting materials and their respective chemical composition. These parameters, however, can only be varied within a limited range. Thus, a substantial bulk density increase can only be achieved by additional processing steps which lead to densification of the detergent granules.
The art is replete with processes directed primarily to densifying or otherwise processing spray dried granules. Currently, the relative amounts and types of materials subjected to spray drying processes in the production of detergent granules has been limited. For example, it has been difficult to attain high levels of surfactant in the resulting detergent composition, a feature which facilitates production of low dosage detergents. Thus, those skilled in the art have striven for ways in which detergent compositions can be produced without having the limitations imposed by conventional spray drying techniques. To that end, the art is also replete with disclosures of processes which entail agglomerating detergent compositions. For example, attempts have been made to agglomerate detergent builders by mixing zeolite and/or layered silicates in a mixer to form free flowing agglomerates. While such attempts suggest that their process can be used to produce detergent agglomerates, they do not provide a mechanism by which starting detergent materials in the form of high active surfactant pastes and dry materials can be effectively agglomerated into crisp, free flowing, highly dense detergent agglomerates.
Additionally for purposes of insuring consumer satisfaction, it is important for the resulting agglomerates to have a controlled median particle size such that the detergent agglomerates do not segregate by size in the final detergent product box. However, controlling the particle size of the agglomerates in typical agglomeration processes has been a problem since the particle size ultimately formed is extremely sensitive to slight variations in a wide range of process factors such as equipment operating temperatures, and the temperature and compositions of the detergent ingredients. This problem is especially exacerbated in the event that certain highly viscous surfactant pastes are used in the agglomeration process. Such surfactant pastes lend themselves to being affected by environmental factors before and during processing, all of which cause great fluctuations in the ultimate size of the resulting agglomerates. As a consequence, it would be desirable to have an inexpensive method by which the agglomerate particle size can be effectively controlled, especially in large-scale production facilities.
Accordingly, despite the above-described disclosures in the art, there remains a need for a process for effectively regulating the particle size of high density detergent agglomerates produced by an agglomeration process which produces such agglomerates directly from starting detergent ingredients. Also, there remains a need for such a process which is inexpensive and can be easily incorporated into large-scale production facilities for low dosage or compact detergents.